3.4.5 How Can I Find All of the Slaves Attached to My Master Server?

When you have a topology that has grown over time - slaves have
been added from time-to-time, it may not be so easy to remember
which servers are connected as slaves.

Most often you want to know the state of those slaves
at-a-glance. Rather than connect to each slave individually, it
would be nice to know what the state of each slaves threads
using a single command.